Material discharge gun



May 9, 1967 O. RHODES MATERIAL DISCHARGE GUN Filed Aug. 24, 1964 0/27er'Rhodes I N VE NTOR.

BY z/wpw v United States Patent 3,318,530 MATERIAL DISCHARGE GUN OmerRhodes, Houston, Tex., assignor to Clemtex Ltd., Houston, Tex., alimited partnership Filed Aug. 24, 1964, Ser. No. 391,720 1 Claim. (Cl.239-117) This invention relates to a pneumatic gun for dischargingmaterials of a semi-fluid nature and more particularly to air brushes ofthe type adapted for spraying coating materials such as metalliccoatings of the type such as zinc coatings. These coatings act assacrificial protective coatings for steel and this process is sometimesreferred to as cold galvanizing.

One of the problems associated with the operation of this type of spraygun is that material being sprayed will quite often build up as aresidue on the surface of the gun adjacent to the orifice which emitsthe material to the atmosphere. This build up of material not onlydistorts the volume of material being emitted or ejected from the gunbut can also be of such extent that When it is desired to terminateoperation of the gun, the material will continue to flow from theopening causing great economic loss. This is usually caused by thematerial build up fouling or otherwise rendering inoperable the valvestructure which ordinarily closes off the flow of the material.Moreover, the type of material which is contemplated for use withrespect to the instant invention will normally cause severe abrading andthereby render some guns inoperable in a very short time.

The prior art is replete with examples of various gun devices which havebeen developed and which have one or more of the aforesaid deficiencies.Many of the prior art guns have needle valves which are designed to sealand close off the emitting orifice. However, these needle valves areparticularly susceptible to the aforesaid fouling. Other prior artdevices have utilized certain flexible butt type valves but they arelikewise adversely affected by the build up of residue of the spraymaterial on the surfaces and valve seats thereof.

Moreover, the straight hydraulic guns of the prior art are notsatisfactory for spraying the metallic coatings such as zinc coatingsbecause the extremely high pressures at which these type of guns operatecauses the zinc or other metal to separate out from the carrier.

It is therefore an objective of the instant invention to provide animproved pneumatic spray gun wherein the aforesaid deficiencies areovercome with a minimum of maintenance problems.

Examples of prior art patents which reflect the general state of the aninclude the following US. Patents: 1,969,- 205, 2,577,437, Re. 19,907,1,321,014, 2,457,993, 2,105,- 903, 2,584,943, 1,081,102, 1,736,356.

Briefly stated, the instant invention is a pneumatic spray gun forspraying a coating material, which spray gun has what will be describedas a gun body. This gun body is provided with a nozzle end and at leastone passage through the body for receiving a pressurized gas such asair, and for discharging the gas in a predetermined pattern out thenozzle end.

Inlet means are connected to the gun body for receiving the coatingmaterial under pressure, normally in the range of about fifteen poundsto fifty pounds per square inch. A cylinder is connected to this inletmeans for receiving the coating material. One end, i.e., the forwardend, of the cylinder has a portion with a reduced diameter, which end ismounted for emitting the material to the atmosphere and through the gaspattern. The other end of the cylinder is provided with a frusto conicalshaped valve seat. A frusto conical shaped valve of resilient materialsuch as rubber issupported adjacent to the valve seat and adapted forseating therein in a closing relationship. This valve is mounted on avalve stem, which stem is axially aligned with the central axis of thecylinder. There is also provided means for moving the valve and valvestem axially with respect to the valve seat whereby said valve is movedto and from a closed position.

Biasing means are also provided for normally urging the valve and valvestem to a closed position when the gun is not being operated. The foreend or front end of the valve stem is providing with an extension needlewhich projects forwardly in the cylinder and has a point which isadapted to move in and out of the reduced end of the cylinder in a loosefitting relationship during opening and closing of the valve. Hence, thediameter of the tip of the pin is smaller than the diameter of thereduced end of the cylinder which forms the emitting orifice. Thepurpose of this needle is to maintain an opening through this emittingorifice despite a certain amount of residual build up of spray material,and also prevents excessive build up in the orifice.

Reference to the drawings will further explain the invention, wherein:

FIG. 1 is a side elevation view generally in central section of oneembodiment of the instant invention.

FIG. 2 is an enlarged fragmentary view of a portion of the cylinder andvalve arrangement of the instant invention.

FIG. 3 is a view taken at line 3-3 of FIG. 2 showing the mounting of thevalve in relation to the valve stem.

Referring to FIG. 1, one embodiment of the instant invention will beexplained in detail. There it will be seen that gun body 11 is providedwith air inlet means in the form of air inlet nipple 12 connected to airtube 13 which is, of course, connected to a suitable supply ofpressurized air, or gas, which will be used for the spraying operation.Nipple 12 communicates with air duct 14 which leads up through thehandle of gun body 11 to lower cylinder 15. Cylinder 15 has springbiased air valve 16 mounted therein and which is actuated by theoperation of trigger 17 operating against valve rod 18 working throughappropriate packing. When valve 16 is unseated air is supplied throughappropriate channels communicating with the annular space 19 whichsurrounds gasket housing 20 which is mounted in middle cylinder 21.

Gasket housing 21 supports plunger 22 therein which is normally biasedto the left as viewed in FIG. 1 by spring 23. Plunger 22 connectsthrough gasket housing 20 to piston 24 which in turn is connected tovalve rod 30. Piston 24 is engaged by trigger 17 when trigger 17 ismoved rearwardly.

Air is then supplied upwardly to upper cylinder 31 through appropriateconduits. Mounted inside of upper cylinder 31 is air control sleeve 32which forms two channels to the nozzle end of the gun as will now 'beexplained.

Sleeve 32 is provided with a plurality of small ports 33 whichcommunicate with the internal chamber 36 which extends forward throughsleeve 32. The passage of air through chamber 36 is controlled by needlevalve 34 which in turn is adjusted by dial 35 mounted on the back sideof gun body 11. Air is thus admitted to internal chamber 36 of sleeve32. The front end of sleeve 32 is threadably connected to spray head 41,the details of which will now be explained.

While spray head 41 will be described as being unitary, it is to beunderstood that it could be made of a plurality of parts operablyconnected together. The lower end of spray head 41 is provided withmaterial inlet means in the form of tube 42 which projects downwardlyfrom the gun. Tube 42 communicates with cylinder 43 which is in the formof a sleeve with a cylindrical opening therein which is generallyaxially aligned with valve rod 30. Valve rod passes through a rearwardlyextending portion of spray head 41 which is held in a ring 40, which isattached to and forms a part of gun body 11. This rearwardly extendingportion of spray head 41 supports packing 39 and packing nut 38 throughwhich valve rod 30 moves.

The fore end of the cylindrical opening in cylinder 43 has a reducedarea formed by fluid tip 44 which is threadably secured to spray head 41as best seen in FIG. 2. There it will be observed that cylinder 43 isunobstructed and that fluid is emitted out orifice 45 formed in theforward end of fluid tip 44. Hence, it may be said that orifice 45 has adiameter less than the diameter of cylinder 43. The other end, i.e., therearwardly end, of cylinder 43 is provided with a frusto conical shapedvalve seat 46 which is generally concentric with the central axis ofcylinder 43. It is an important feature of this invention that valveseat 46 is frusto conical in shape as'will be explained hereinafter.

Mounted on valve rod 30 and held adjacent to valve seat 46 is a frustoconical shaped resilient valve 47 which may be made of rubber or thelike. Valve 47 is held in position by valve retainer washer 48 on theback side thereof and lock washer 49 on the front or leading sidethereof. One important feature of the present invention is that thefrusto conical section of valve 47 is generally of a longer axial lengththan the axial length of valve seat 46. Hence, valve 47 has a relativelylarge seating area for contacting and closing with valve seat 46. Thebeveled surface or frusto conical shape of valve seat 46 also permitsthe flow of fluid. there past which helps to cleanse the valve seat areaand reduces the amount of material residue build up thereon. Inaddition, since valve 47 is of a resilient material, it will easilyconform to the surface of a valve seat 46 even if there is a slightmaterial build up thereon. Further, the fact that the axial length ofthe frusto conical section of valve 47 is longer than the axial lengthof valve seat 46 allows both for any wear on valve 47 and anyundesirable build up of residual spray material on valve seat 46. Theseare some of the important features of the invention and which provide apositive closing action under normal operating conditions when sprayingmetallic base coatings.

Normally, valve 47 will be biased to the closed position and seatedagainst valve seat 46 by operation of spring 23 acting on plunger 22,piston 24 and rod 30 when the tool is not in operation as is shown inFIG. 1.

Spray head 41 has threadably attached around the end thereof retainerring which is adapted to secure and hold in place air cap 56 having airdischarge orifices 57 which are for projecting air therefrom in apredetermined pattern. In addition, fluid tip 44 has an annular flange58 which secures annular sleeve 59 in position. Sleeve 59 has spacedthereabout annular bafile rings which help to disperse the air to all ofthe orifices 57. Sleeve 59 also forms on the inside thereof an annularchamber which communicates with upper cylinder 31 and providespressurized air through an air orifice in air cap 56, which air orificesurrounds the forward end of fluid tip 44 which forms fluid orifice 45.

In operation of the gun, and starting from the closed or inoperativeposition, material to be sprayed is supplied through tube 42 under thedesired pressure, usually in the range of fifteen pounds to fifty poundsper square inch. In addition, pressurized air is applied through airtube 13 to cylinder 15. Upon actuation of trigger 17 air issimultaneously applied upwardly for passage through chamber 36 of sleeve32 and then out of orifices 57. At the same time air is applied alongthe surface of upper cylinder 31 to the chamber surrounding fluid tip44, through axial openings 60 provided in flange 58, and then outwardlyaround the forward end of fluid tip 44 and past orifice 45, therebyforming another air pattern I for atomizing and dispersing the coatingmaterial.

As trigger 17 is moved rearwardly it also moves piston.

24 and valve rod 30 rearwardly thereby unseating valve 47. At this pointthe pressurized material will flow upwardly through tube 42, past washer48, and through peripheral notches 61 provided therein. As the materialis forced out orifice 45 under pressure, it will contact the airpatterns established by the air being discharged from the nozzle end ofthe gun and thereby projected to the desired spray pattern.

It will be observed that the forward end of rod 30 has attached theretoneedle 62, the tip of which is of a smaller diameter than orifice 45,and hence fits therein in a loose fitting arrangement. When the spraygun is not in operation, valve 47 is seated in valve seat 46. Uponactuation of trigger -17, needle 62 is withdrawn from orifice 45 at thesame time that valve 47 is unseated. The purpose of needle 62 is toprevent stop-up of orifice 45 by residual spray material during closedown or non-' operation of the tool. Needle 62 is supported on rod 30such that cylinder 43 is maintained in an unobstructed condition so thatspray material may easily flow therethrough.

The instant invention provides many advantages over the prior art. Forexample, a spray gun constructed according to the present invention hasoperated for a long period of time with few maintenanceproblems, whereasa prior art gun heretofore used for this purpose without the novelelements of the present invention was susceptible to malfunctioningafter a short period of operation. For example, the gun of the instantinvention has sprayed in excess of 800 gallons of a coatingmateria-l,such as zinc spray coating, without failure or malfunctioning, whereasthe use of a similar gun without the novel elements of this inventionsprayed only five gallons before shut down, disassembly, and cleaning ofthe gun was required. .In the case of this prior art gun, the build upof residue material in the valve structure prevented the cut off of theflow of the spray material during non-operation. Hence, there was greatloss of material from the gun when not spraying. In addition, there wasmuch loss of time in disassembling the gun to correct thismalfunctioning.

One advantage of the instant invention is that the novel shape andarrangement of resilient valve 47 in relation to valve seat 46 providesa very positive closing of the fluid material flow. In addition, theresiliency of valve 47 accommodates any slight build up which may occuron valve seat 46. Moreover, build up of residual spray material on valveseat 46 is reduced because of the tapered or frusto conical shape ofseat 46. It is thought that the fluid flow through, along, and past thebeveled surface of valve seat 46 assists in cleaning therefrom thematerial that may build thereon. In addition, needle 62 projects intoorifice 45 during non-operation of the tool to prevent the hardening ofany residue of spray material therein. Hence, when operations areresumed with the gun, an immediate opening is provided through orifice45. This is more than a cleaning action on the part of needle 62 in thatit also provides a continuous opening through orifice 45 upon removal ofneedle 62 therefrom. Depending upon the particular material beingsprayed, orifice 45 will generally have a diameter of at least of aninch or larger.

For purposes of convenience, gun body 11 and spray head 41, togetherwill sometimes be referred to as a gun body generally.

Further, for purposes of convenience cylinder 43 and fluid tip 44 maysometimes be referred to together as a cylinder for receiving thecoating material to be sprayed.

In this connection, and as explained above, spray head 41 and associatedelements may be unitary or a plurality of parts which when assembled,assume the form of the invention described. Hence, in someinstances,-prior art guns may be converted to guns which embody theinstant in ention by use of a conversion kit having the necessaryelements and adaptors for the spray gun of this invention.

Further modifications may be made in the invention as particularlydescribed without departing from the scope of the invention.Accordingly, the foregoing description is to be construed illustrativelyonly and is not to be construed as a limitation upon the invention asdefined in the following claim. 1

What is claimed is:

A pneumatic spray gun for spraying a metallic coating material, thecombination comprising:

a gun body having a nozzle end and at least one passage therethrough forreceiving pressurized air and for discharging said air in apredetermined air pattern out said nozzle end,

inlet means connected to said gun body for receiving said coatingmaterial under pressure,

a cylinder forming an unobstructed chamber connected at a generallyright angle to said inlet means for receiving said coating material, oneend of said cylinder having a reduced diameter forming a dischargeopening and mounted for emitting said material through said air patternand the other end of said cylinder having a frusto conical shaped valveseat concentric with central axis of said cylinder and positionedsubstantially rearward of said discharge opening and adjacent said inletmeans with the smallest diameter of said valve seat being at least twicethe diameter of said discharge opening, whereby a given quantity ofspray material will pass therethrough in the open position at asubstantially lower velocity than through said discharge opening,

a frusto conical shaped valve of resilient material supported adjacentto said valve seat and for seating therein in a closing relationship,the axial length of the frusto conical portion of said valve being of agreater length than the axial length of said valve seat,

said valve being mounted on a valve stem axially aligned with saidcylinder,

means for moving said valve and valve stem axially with respect to saidvalve seat, whereby said valve is thereby opened and closed,

resilient biasing means for normally urging said valve and valve stem toa closed position when said gun is not being operated, and

an extension needle connected to the front end of said valve stem andprojecting into said discharge opening in loose fitting relationshipwhen said valve is in the closed position, whereby an opening ismaintained through said discharge opening even during times when coatingmaterial residue tends to build up therein.

References Cited by the Examiner UNITED STATES PATENTS 1,661,150 2/1928Birkenmaier 239-117 2,172,193 9/1939 Downs 239-597 2,236,551 4/1941Striegel 239407 2,705,663 4/1955 Gilbreath 239590.3 3,111,271 11/1963Lofgren 239117 3,198,435 8/1965 Ullrnan 239117 M. HENSON WOOD, JR.,Primary Examiner.

R. S. STROBEL, Assistant Examiner.

